Stoker



C. W. BROS Jan. 14, 1941.

STOKER Filed NOV. l5, 1937 Patented Jan. 14, i941 UNITED STATES .P'rrrl-:lvr 'OFFICE Chester W. Bros, Minneapolis,y Minn., assignor to Wm. Bros Boiler & Manufacturing Company, Minneapolis, Minn., a, corporation of Minnesota i Applicatie November 15,1937, seal No. 174,607 6 claims. (Cl. 11o- 102) This invention relates to nev and useful improvements in'fuel feeding apparatus, such for example, as stokers.

Heretofore it has been found to be extremely diicult and even impractical to burn such waste fuels as wood shavings, wet hogged fuel, oat hulls, chaff, or sinilar material ina conventional stoker in combination with coal. In the past this waste fuel has been'spouted directly into l" the furnace where it piles up in high cones, making eicient combustion of both the coal and thewaste fuel impossible. This by-product fuel is either fed into the furnace by an automatic waste fuel stoker, such as illustrated in the drawl5 ing, or by direct means froma cyclone 0r c'onveyer as the fuel is made in the plan-t. Usually the latter means are used, to eliminate the cost of the Waste fuel feeder, and therefore the Waste .material dumps in slugs completely upsetting the 2" normal fuel bed because of its piling up action.- The material coming down a small diameter pipe inslugs prevents the air from penetrating the fuel as it drops on to the grate so practically no burning takes place in suspension.

'I'he difficulty is that a.' great percentage of the by-product material dropsthrough the furnace and lands on the grate, accumulating in high cones. AThis causes an uneven accumulation of coal and waste fuel on the Stoker or f" grate surface tending to fuse the coal into elink-- ers because of the catalytic action of Wood4 and coal When agitated.

If this material could be burned in suspension, l

its efficiency of combustion would be high and 'if' it would not have a tendency to mix 0n an agitated fuel bed 1as presented by an underfeed stoker. The overfeed sprinker type stoker burn'- ing coal burns a large percentage of its coal in suspension, and if the principle of the sprinkler W type Stoker is applied to burning this waste fuel, the type of combustion would be approximately the same as that of coal.. I have found that when waste fuel is fed onto the revolving rotor of an overfeed stoker with rotor blades of 45 different angles toprovide for even spreading of the coal throughout the grate that the terrific slapping action of the rotor blades evenly blasts the waste fuel into the furnace in a fan shape permitting the air for combustion to surround f1" each fuel particle, therebyl causing much of the fuel to be burned in suspension. In the burning of dry wood shavings, such as res-ult from the operation `of a sash and' door or furniture factory, approximately ninetyffive percent of the 55 fuel never lands on the grates-t being burned -teriaL in the furnace proper similarly to pulverized fuel. It is therefore essential that the fuel be thor= oughly aerated, when-'discharged vinto thel combustion chamber, ificomplete and thorough combustion is to be obtained.

With such wet fuels as hogged fuel of about eighty percent moisture, a much greater percentage drops on the grate, but in passing in its flight from the rotor through the `incandescent furnace much of the moisture is driven off permitting the remaining dried material to burn easier on the grate. When burning fuel with a highmoisture content, it is imperative thatthe temperature of the furnace-be maintained by coal fed through the Stoker in the conventional manner. When burning dry waste fuel, coal need not necessarily be supplied'to maintain ignition,

but usually coal is fed in order to maintain the,

required .steam demands Y, and steam pressure. Undoubtedly in most` cas-es the Waste fuel will be an auxiliary feed, with the coal maintaining a majority of the fuel fed to the furnace.

`I- have f-ound that Waste fuel, such as wood or oat.hulls, when burned alone in a furnace will accumulate, in a honeycombed mass to considerable height, if fed into the combustion chamber by pipe or spout, thereby interfering with the draft. A great advantage of feeding the waste fuel into the combustion chamber simultaneously with the coal, withthe overfeed sprinkler type of stokerjis that the waste fuel is thoroughly aerated, and the c'oal particlesconstantly bombard the material on the grate, preventing any such accumulation of piles o'f ma- Further, the fuel bed'is not overturned or. agitatedas in. an underfeed Stoker so that the formation of sticky clinkers is almost completely eliminated.

An object of the present invention, therefore, is to. provide a fuel feeding apparatus for a furnace, comprising means for simultaneously or vintermittently delivering into the furnace, a plurality of .separate fuels of different characteristics.

A further object is to provide a, fuel feeding apparatus comprising a fuel distributor, to which a plurality of fuels having different characteristics are simultaneously delivered from separate' sources, and whereby said fuels may be intermixed and aerated by said distributor, simul even fuel bed on th'e mean-s whereby sli-avings or other such fuels may be delivered to the m'iual fuel distributor of the rotor simultaneously with the coal. whereby said diil'erent fuels are thoroughly intermixed before delivery into the combustion` chamber of the furnace.

A further and more speciiic object is to provide avstoker of the overfeed type, comprising a rotary fuel distributor. a coal hopper having means for controlling and regulating the delivery of' the coal to the distributor, and having an vauxiliary fuel feed conduit whose discharge end is disposed in proximity to the discharge of the fuel hopper, whereby the two diiferent fuels may be simultaneously delivered to the rotor, and by the rotary action of which they are thoroughly intermixed and simultaneously delivered into the combustion chambel` of the furnace, in the form of a readily combustible fuel mixture.

A further object is top rovide -a fuel feeding apparatus adapted to simultaneously feed coal and shavings 'into a furnace in such manner that particles of coal are constantly being .precipitated onto the shavings which may tend to accumulate and pile up on the grate, whereby the shav- .ings and ash on the grate are constantly bombarded and disrupted, thereby to maintain an grate to produce emcient combustion.

Other objects of the invention will appear from the following description and accompanying drawing ,and will fbe pointed out in rthe annexed claims. f 1 In the accompanying -drawing there has been disclosed a structure designed tocarry out the various objects of the'invention, but it is to -be understood that the invention is not confined-l to` the exact features `shown as various changes may" be Amade within the scope of the claims which follow. i

The single figure in the drawing illustrates a portion of a stoker with the invention embodied in" the construction thereof.

' In the accompanying drawing, there is illustrateda portion of-a conventional furnace comprislng a front face plate or wall 2, shown secured to vthe usual fire-proof wall 3l of the combustion chamber* 4 of the furnace. The usual grate 5 is shown defining the bottom of the combustion chamber 4, and a door 6 is shownV in the front wall of the furnace, whereby access may be had to the grate 5.

The stoker is shown comprising a suitable frame "I, secured to the front .Wall of the furnace and having an opening 8 therein, through-which the fuel isfedinto the 'combustion chamber by. the stker. A suitable fuel distributor, generally indicated by the numeral 9, is shown mounted beneath the opening 8, and is supported by a suitable shaft II-,driven from va suitable power de-.

vice, not shown in the drawing. A casing I2 is shown secured to the frame 'I- and provides a closure for the lwer portion of the fuel distributor 9.

'I'he supporting frame 1 of the stoker extends outwardly from the front of the furnace and has a suitable hopper I3 mounted thereon, the bottom of which is showndened by an adjustably mounted feed plate I4, supported upon a skeleton frame I5. The skeleton frame- I5 may or may not be integrally formed with the main support ing frame 1 of the Stoker. fThe discharge edge I6 o fthe feed plate I4 is disposed over the fuel di's-` tributor or rotor 9, and is adjustable with respect thereto by longitudinal movement-of the feed.

plate I4 by manipulation' of the adjusting screw `to the rotor 9,

. of which communicates `vided 'with a feed auger I1. This adjusting screw is supported in the por-J tion I5 of the stoker frame, and is heldagainst longitudinal movement in the frame I5 by a co1- lar I8. The adjusting screw is freely rotatable in the supporting frame and has a threaded connection ,with the feed plate I4 by means of a threaded lug I9 secured thereto.

The fuei in the hopper ,is is delivered to the* rotor 9 by reciprocal The feed shoe is mounted forreciprocal movement over the feed plate I4, -by an arm 22 having a link 23 operatively connecting' it with the feed i shoe, as clearly illus'trated. The arm 22 is shown supported upon a suitable shaft 24, to which rocking movement may be imparted by a 'connection 25, pivotally connected to a small arm 26 provided f on the arm 22.

movement of a stepped feed I shoe, generally indicated by the numeral 2| vention, and as illustrated in the accompanying drawing, an auxiliary fuel conduit 28 is shown interposed between the front wallof the furnace and the adjacent .wall of the hopper I3. The discharge end 29 of the fuel conduit 28 is disposed in close proximity to the discharge opening. 21 ofy the hopper I3,'and is `so arranged with respect that the fuel discharging through the conduit 28, will be delivered to the rotor simultaneously with the delivery of the coal therey to from the hopper I3. The two different hfuels thus delivered to the rotor or fuel distributor,. are intermixed by the'rotative action of the rotor 9,` whereby a highly combustible fuel mixture is provided which, when delivered into the combussubstantially completely consumed.

The shavings delivered to conduit 28 may be received. head cyclone or hopper 3|, be provided with a suitable conveyer 32, one end with the conduit 28, as conveyor 32 may bepro- 33 driven by a suitable belt 34 connected to a source of power, not shown. Variation in the speed of the auger 33 may control-the delivery of shavings to the rotor 9, as will readily lbe understood.

The invention is comparatively simple, and whenl used in connection with a coal feeding stoker, makesit possible to burn shavings and/or other. similar materials, together with coal, without waste. By intermixing the shavings with the coal by the action ofthe rotor 9, the resultant mixture is thoroughly aerated, whereby, the shavings may be efficiently burned, because` the the rotor 9 from the from a suitable overclearly illustrated..` The two fuels provide a readily combustible fuel mix- .into the furnace simultaneously with the coal, is

that pieces of coal are constantly being peppered against the partially burned shavings precipitated onto the grate, as illustrated at 35 -in the y l drawing. By thus pepperihg the shav'ings` and ash deposited on. the grate withv pieces'of coal,

tion chamber 4 of the furnace, is readilyvand which may, if desired,

the shavings and ashes on the grate are constantly being bombarded or broken up,` whereby culation of air through the grate, essential in' order to obtain complete and eilcient combustion.

In the drawing I have shown the auxiliary fuel supply conduit 28 as being made independently of the stoker. It is to be understood that I do not Wish to be limited to the specific construction shown in the drawing as obviously, various changes may be made in the construction thereof without departing from the spirit of the invention and the scope of the claims.

I claim as my invention:

l. An over-feed stoker for feeding waste fuel and coal into a furnace, comprising a rotary fuel distributor, means for separately feeding coal directly to the fuel distributor in an approximate vertical direction, and means for separately feeding waste fuel material directly to the fuel distributor in an approximate vertical direction, said rotary fuel distributor due to its rotation intermixing the coal and waste fuel material and showering it in a direction which is approximately at right angles to said feed directions as an aerated mixture of the two fuels into the furnace.

2. An over-feed stoker for feeding waste fuel and coal into a furnace, comprising a frame secured adjacent the furnace, a casing secured to the frame, a rotary fuel distributor mounted in said casing, means adjacent the side of the casing for separately feeding coal directly to the fuel distributor, a vertically disposed conduit provided above the fuel distributor for separately feeding waste fuel material directly to the fuel distributor, and means for feeding waste fuel into the vertical conduit, said rotary fuel distributos' duo to its rotation intermixing the coal and waste fuel material and showering it as an aerated mixture of thetwo fuels into the furnace.

3. An over-feed stoker for feeding waste fuel and coal into a furnace, comprising a frame secured adjacent the furnace, a casing secured to the frame,.a fuel distributor mounted to rotate in said casing, a. coal hopper, means beneath the coal hopper and communicating with the casing for separately feeding coal directly to the fuel distributor, and a conduit disposed vertically above thefuel distributor and having means for separately feeding waste fuel material directly to the fuel distributor, said fuel distributor due to its rotation intermixing the coal and waste fuel material and showering it as an aerated mixture of the two fuels into the furnace.

4. An over-feed stoker for feeding waste fuel and coal'into a furnace, comprising a rotary fuel feeding coal laterally and downwardly to the fuel distributor,and means provided above the` fuel distributor for separately feeding waste fuel .material directly by gravity to the distributor,

5. An over-feedstoker according to claim 4, in

which the means for separately feeding the waste fuel material includes a vertical conduit and the means for separately feeding the coal includes a lY under the vertical conduit whereby a portion of the waste fuel material falling by gravity in its conduit will fall on thel coal on the feed plate as the latter material is fed to the distributor.

distributor, means for separately and directly laterally disposed feed plate which projects part- 1 l 6. An over-feedl stoker according to claim 4, l

in which the means for feeding the coal includes a plate and a stepped feed shoe, and in which means are provided to reciprocate the feed shoe n on the plate to feed the coal to the distributor. CHESTER. W. BROS. 

